The world number three opted out of the U.S. Open tune-up event in Montreal with the same strain that has limited his service motion and forced him to forfeit his Wimbledon semi-final last month.
"(Flying) tomorrow to Cincinnati," the Spaniard posted alongside a photo of himself shirtless and smiling.
"Very happy to play again in Cincy."
Nadal, who has won a men's record 22 major titles, will be the only one of tennis' Big Three in the draw of the hardcourt tournament as rivals Roger Federer and Novak Djokovic will both be absent.
Federer is still undergoing rehab after undergoing knee surgery while Wimbledon champion Djokovic is unable to compete in the North American tournaments due to his refusal to get vaccinated against COVID-19, which prevents him from entering the two countries.
